Registration Dossier

Environmental fate & pathways

Adsorption / desorption

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

In a key study (BASF SE, 394801, 2015) according to OECD 106 (2000) the adsorption and desorption behaviour of the radiolabelled test substance was determined on four US soils and two European soils, which covered a range of pH (in water) from 5.5 to 7.8, a range of organic carbon content from 0.81% to 1.40% and four different USDA textural classes: silt loam, loam, loamy sand and sandy loam. The resulting Freundlich adsorption coefficients, KF, ranged from 6.66 to 30.11 mL/g. The KFoc values ranged from 765 to 3708 mL/g with a mean of 1673.9 mL/g. The 1/n values ranged from 0.71 to 0.84. For desorption isotherms, the KF ranged from 10.54 to 33.95 mL/g and the KFoc values ranged from 1205 to 4119 mL/g for the six soils. The higher desorption values indicate the test substance is not readily desorbed following adsorption to soil. Simple adsorption coefficients, Kd, for the highest isotherm concentration tested ranged from 4.49 to 20.17 mL/g, with Koc values ranging from 516 to 2439 mL/g.

Key value for chemical safety assessment

Koc at 20 °C:
1 673.9

Additional information

In a study (BASF SE, 394801, 2015) according to OECD 106 (2000) The adsorption / desorption behavior of the radiolabeled test substance (pyranone-6-14C radiolabel) was investigated using six soils, four from the US and two from Europe. The six soils covered a range of pH (in water) from 5.5 to 7.8, a range of organic carbon content from 0.81 % to 1.40 %, and four different USDA textural classes: loam, loamy sand, sandy loam and silt loam.

 For the determination of the adsorption isotherm, five different concentrations (nominal 8.00, 4.00, 2.00, 0.50 and 0.08 mg/mL) of the test item in 0.01 mol/L CaCl2 solutions were used. The ratio of soil versus test solution was 1:5 and the adsorption equilibrium time was 48 hours for the six soils. All samples were equilibrated in the dark at 20 ± 2 °C. Desorption of the adsorbed test substance following the equilibrium phase was determined through two desorption steps, each for 48 hours using clean 0.01 M CaCl2 solution. The concentrations of the test substance in the adsorption solution, desorption solutions, and soils extracts were determined by liquid scintillation counting. The stability of the test substance in the test system was confirmed by radio-HPLC analysis of the sample solutions and extracts at different phases. The mass balance of the radiolabeled test substance for the test soils ranged from 90.4 % (CA soil) to 94.9 % (LA soil) of the total applied radioactivity (TAR).

 The following adsorption and desorption parameters were measured for the radiolabeled test substance in each soil: distribution coefficients Kd and Koc at five concentration levels, the Freundlich coefficient KF, the Freundlich exponent 1/n, and the corresponding KFoc values. 

The resulting Freundlich adsorption coefficients, KF, ranged from 6.66 to 30.11 mL/g for the six soils. The KFoc values ranged from 765 to 3708 mL/g with a mean of 1673.9 mL/g. The 1/n values ranged from 0.71 to 0.84. For desorption isotherms, the KF ranged from 10.54 to 33.95 mL/g and the KFoc values ranged from 1205 to 4119 mL/g for the six soils. The higher desorption values indicate the test substance is not readily desorbed following adsorption to soil. Simple adsorption coefficients, Kd, for the highest isotherm concentration tested ranged from 4.49 to 20.17 mL/g, with Koc values ranging from 516 to 2439 mL/g.

[LogKoc: 3.22]